Retrospective Surveillance for Drinking Water-Related Illnesses in Canada, : Final Report

Transcription

1 Retrospective Surveillance for Drinking Water-Related Illnesses in Canada, : Final Report Novometrix Research Inc. August 29th, 2009 Jeff Wilson PhD Jeff Aramini PhD Stephanie Clarke MSc Monica Novotny PhD Melanie Quist MSc Victoria Keegan MSc Production of this report has been made possible through a financial contribution from the Public Health Agency of Canada through the National Collaborating Centre for Environmental Health. The views expressed herein do not necessarily represent the views of the Public Health Agency of Canada or the National Collaborating Centre for Environmental Health. RR1 Moffat, Ontario, Canada L0P 1J0 Jeff_Wilson@Novometrix.com Tel: (519) Fax: (519)

2 EXECUTIVE SUMMARY Waterborne infections are an important cause of preventable enteric disease in Canada each year. The design of policies and programs for waterborne disease prevention is hampered, in part, by an absence of systematically collected information on the characteristics and causes of waterborne disease events (WBEs). Our objective was to obtain information that would facilitate WBE prevention policies and programs, including: (i) defining the characteristics of WBEs in Canada (ii) describing factors contributing to WBEs (iii) describing current WBE detection and prevention practices and (iv) identifying information needs of front-line public health staff. Representatives from all public health regions across Canada were contacted to obtain information on WBEs (suspected or confirmed) that had occurred between 1993 and 2008 based on recall and their review of available reports. Voluntary telephone interviews using a standardized questionnaire collected information on the factors described. Of 100 attempted contacts, 71 respondents agreed to be interviewed (71% response rate). Forty-seven WBEs were identified. The majority of WBEs identified occurred prior to Giardia and Cryptosporidium were the most common etiological agents, followed by bacteria and viruses. One half of communities experiencing WBEs had surface water as their water source and the majority of surface water was from unprotected watersheds. In terms of water treatment at the time of WBE identification, no water treatment was available for 39% of the communities, disinfection alone was used in 46%, and filtration combined with disinfection was used in 15%. Communities with larger populations tended to use a multiple barrier approach to water treatment. Most regions issued some form of boil order or advisory in response to the outbreak. The proportion of regions using surface water declined post-outbreak while water treatment practices tended to improve. The majority of WBEs occurred in communities having small to medium-sized populations with the exception of those caused by Cryptosporidium which occurred most commonly in larger communities. For the most part, Giardia, bacteria and viruses were the etiologic agents in WBEs that occurred in communities having either no water treatment or disinfection only, while Cryptosporidium-related outbreaks generally occurred in communities having some combination of disinfection and filtration. In WBEs caused by Cryptosporidium that occurred in association with filtration, filtration systems were either old or were affected by some form of system failure. Approximately 50% of communities experiencing WBEs did not monitor water quality in the incriminated water system. Regions often cited multiple factors that contributed to WBEs, such as inadequate treatment, lack of source protection, and precipitation. In response to outbreaks, 65% of regions changed the water source while 56% upgraded or changed the treatment system and 30% changed or improved policy, reporting, monitoring, or a combination thereof. This investigation provides a detailed description of WBE characteristics in Canada. These characteristics suggest several key opportunities to improve drinking water management and mitigate known risks for waterborne disease and WBEs: 1. Improve water treatment effectiveness and water quality monitoring Novometrix Research, Inc. Page 1 of 40

3 2. Enhance waterborne disease surveillance and communication between stakeholders 3. Establish WBE prevention plans and policies that include watershed management and which take into account the potential for extreme weather events and the impact of global climate change 4. Seek appropriate expert advice in the event of WBEs 5. In each of the above, place special emphasis on small to medium sized communities The occurrence of WBEs is an important factor in the motivation to improve drinking water management based on interview responses; collection and dissemination of information on WBEs should be encouraged. Novometrix Research, Inc. Page 2 of 40

4 INTRODUCTION Waterborne infections constitute an important cause of preventable enteric disease in Canada each year. The design of policies and programs for waterborne disease prevention is hampered, in part, by an absence of systematically collected information on the characteristics and causes of waterborne disease events (Schuster et al, 2005). Surveillance for endemic waterborne infections is problematic, in part because it can be difficult to accurately determine the source of individual cases of infection and the pathogens involved in waterborne disease can be acquired from a variety of other sources such as food, person-to-person transmission, and animal exposure. Though perhaps not constituting the majority of waterborne disease cases, outbreaks of waterborne disease (Waterborne Disease Events: WBEs), do provide a window into sources, health impacts, and factors contributing to waterborne illness under conditions where disease can be verified to be due to consumption of contaminated drinking water, through laboratory or epidemiologic evidence (Hrudey and Hrudey, 2004). Unfortunately there is no national surveillance system in Canada for waterborne disease outbreaks, and approaches to collection of information on such outbreaks are not standardized. Information that is collected is often not published or not distributed beyond the relevant regional public health authorities, and is often incomplete. Schuster et al (2005) noted these issues in their review of available published information on waterborne disease outbreaks in Canada between 1974 and To address these deficiencies, this investigation was undertaken in order to obtain detailed, standardized information on past waterborne disease outbreaks between 1993 and 2008 through in-depth interviews of relevant front-line environmental health professionals working in each pubic health authority in Canada. Information collected included characteristics of WBE and associated source waters, the nature of water treatment and WBE prevention programs, demographic information and health outcomes related to WBEs, and information needs related to WBE prevention. Our objective was to obtain information of direct relevance to the design of WBE prevention policies and programs by (i) defining the characteristics of WBEs in Canada including etiologic agents involved, temporal and geographic patterns, demographic characteristics of cases and health outcomes (ii) describing factors contributing to WBEs including the nature of source waters and their treatment and predisposing factors such as weather, water contamination and human error (iii) describing current WBE detection and prevention practices and (iv) identifying information needs related to WBE prevention for front-line public health staff. For the sake of completeness, this investigation included acute illness related to exposure to chemical and radiological agents in addition to infectious organisms. Novometrix Research, Inc. Page 1 of 40

5 METHODS Representatives from all public health regions across Canada were contacted to obtain information on drinking water-related disease events (Waterborne Disease Events: WBEs), suspected and confirmed, that had occurred between Relevant individuals received an initial and telephone call and were asked to identify the appropriate person to speak with regarding waterborne disease outbreaks. The appropriate individuals were sent information by explaining the study and requesting an interview. Those who did not respond were subsequently contacted by telephone. Telephone interviews were arranged for those willing to participate. Participants were interviewed using a standardized questionnaire to obtain information for all outbreaks experienced in the relevant region over the study period with respect to (i) characteristics of WBEs (ii) water source characteristics at the time of the WBE and at the time of the interview (iii) water treatment and distribution at the time of WBE and at the time of the interview (iv) demographic information and health outcomes related to WBEs (v) factors contributing to and outbreak control measures related to WBEs (vi) WBE prevention programs or policies stemming from the WBE (vii) programs in place to detect or prevent WBEs and (viii) information needs with respect to WBEs. Public health regions reporting no WBE over the study period were interviewed using a condensed questionnaire that focused on current water treatment systems and WBD prevention programs and excluded questions related to specific WBE. Participants were asked to examine and have on hand relevant outbreak reports to assist in their responses. The questionnaires are shown in Appendix I. For the purposes of this study, WBE was defined as a suspected or confirmed acute illness related to exposure to biological, chemical or radiological agents from drinking water and involving two or more individuals. Also included were such events involving a singe individual where a clear point source (eg a private well) could be identified. Questionnaire responses were entered into a database and analyzed using SPSS (16.0 SPSS for MAC ). The analysis included calculation of descriptive statistics (means, proportions etc) and relevant cross-tabulations. RESULTS Compliance Different provinces had a different structure and approach to their waterborne disease outbreak monitoring, depending on whether it was a provincial, a regional, or a combined responsibility. Also, some provincial authorities requested that we interview a more limited number of individuals (who sometimes had familiarity with outbreaks in more than one regional authority) rather than interviewing a representative from each regional authority. This affected our approach to identifying the appropriate individual to be interviewed. For AB, ON, QC, NL, and SK, we contacted every regional health authority directly. For MB and BC, provincial authorities directed us to the appropriate contacts. For PEI, NS, NB, YK, NU, and NWT, a single interview was arranged that covered the entire province or territory. The result was that individuals were identified Novometrix Research, Inc. Page 2 of 40

6 who in total, provided coverage of past WBEs across the country. However, it was not possible in every case to determine precisely which regional authorities were covered by each interview. We attempted to contact 100 different individuals that resulted in 71 successful contacts for a 71% success rate. There were 47 viable WBE interviews by the study end date, although a total of 48 waterborne disease event interviews were conducted (the New Brunswick interview was not complete enough at the deadline to be included). There were 41 shortened interviews with regions that had not had an outbreak. In total there were 88 completed interviews from 100 contacts for 11 of the 12 provinces and territories. Table 1 summarizes the number of contacts made and the number that were successfully interviewed, by province. Note that the number of interviews per province does not necessarily equal the number of successful contacts as some contacts provided interviews for more than one outbreak and some contacts provided information on more than one regional authority. Also note that, in tables of results of single response questions where the total number of WBEs is less than 47, the difference is the result of missing data for the relevant question. Table 1 Distribution of contacts and interviews by province. Contact Success Interview Breakdown Province Successful Contacts Attempted Contacts Success (%) Outbreak Interview Nonoutbreak Interview Total Interviews Alberta British Columbia Manitoba New Brunswick Newfoundland Northwest Territories Nova Scotia Nunavut Ontario Prince Edward Island Quebec Saskatchewan Yukon TOTAL Novometrix Research, Inc. Page 3 of 40

7 Temporal Characteristics of Waterborne Disease Events The distribution of outbreaks by year of onset (Table 2 and Figure 1) reveal that the annual number of reported outbreaks was substantially higher up to and including the year 2000, and lower subsequently. Table 2 Distribution of waterborne disease events (WBE) by year of onset. Year Number of WBE (%) (11) (11) (18) (9) (4) (11) (0) (16) (4) (2) (0) (2) (2) (4) (4) (0) Total 45 (100) Figure 1 Histogram of the distribution of waterborne disease events by year of onset. Novometrix Research, Inc. Page 4 of 40

8 The majority of WBEs began in summer (June-August; 54%) and spring (March-May; 21.7%). WBEs lasted an average of 74 days, with a median of 45 days (range days). The average number of days between the onset of a WBE and its identification was 18.2 (median 18; range 2-120). Table 3 shows the distribution of WBEs by the mechanism through which they were identified. Participants reported that outbreaks were identified most frequently through patient, (35%), laboratory (33 %) or physician (22%) reports. However, respondents also reported that the identification of WBEs often involved more than one source of information. Table 3 Method of waterborne disease event (WBE) identification. Method of WBE Identification Number (%) Patient 16 (35) Lab Reports 15 (33) Physician 10 (22) Complaint Phone Line 3 (7) Pharmacist 2 (4) Water Utility / Municipality 2 (4) Water Regulator 2 (4) Other Public Health Unit 2 (4) Surveillance 2 (4) Other 1 (2) Table 4 shows the distribution of WBE by etiologic agent. Protozoa (Giardia and Cryptosporidium) were the most commonly identified agents, followed by bacteria and norovirus. Two waterborne chemical-related outbreaks were identified: one was due to copper poisoning and the other was related to elevated nitrate levels. Table 4 Distribution of waterborne disease events (WBE) by etiologic agent. WBE Agent Frequency (%) Giardia 10 (21) Cryptosporidium 7 (15) Cryptosporidium & Giardia 2 (4) Toxoplasma 1 (2) Campylobacter 3 (6) E. coli 3 (6) E. coli & Campylobacter 1 (2) Legionella 1 (2) Salmonella 1 (2) S. aureus 1 (2) Total coliform 1 (2) Norovirus 4 (9) Hepatitis A 3 (6) Chemical 2 (4) Not identified 7 (15) Total 47 (100) Novometrix Research, Inc. Page 5 of 40

9 Drinking Water Orders and Advisories A drinking water order or advisory was issued in response to WBEs in the majority of the cases (77%). In 19% of WBEs no order or advisory was instituted, and an order or advisory was already in effect when two WBEs had occurred (Table 5). The majority of drinking water restrictions were boil water advisories (BWA; Table 6). Drinking water restrictions or recommendations were most commonly issued by the medical health officer, local health unit staff member, or a private facility (Table 7). The duration of the drinking water restriction or recommendation was determined for 20 WBEs, and the mean was days with a median of 48 days (range days). Very few WBE involved more than one regional authority; the average number of additional regions involved was less than 1. Table 5 Number of drinking water orders / advisories implemented due to waterborne disease events. Order or Advisory Instituted Number (%) Yes 33 (77) No 8 (19) Order or Advisory already in Place 2 (5) Total 43 (100) Table 6 Type of drinking water restriction and recommendation issued due to waterborne disease events. Type of Restriction or Recommendation Number (%) Boil Water Advisory 25 (71) Boil Water Order 5 (14) Boil Water Advisory & Shut Public Facility 2 (6) Closed Well / Shut Off Water 2 (6) Boil Water Notice 1 (3) Total 35 (100) Table 7 Individuals or agencies declaring drinking water restrictions or recommendations due to waterborne disease events. Individual / Agency Declaring Drinking Water Restrictions or Recommendations Number (%) Public Health Unit Staff or Inspector 9 (32) Medical Officer 4 (14) Private Facility 4 (14) Department of Environment 3 (11) Department of Health 3 (11) Town or City Staff 2 (7) Departments of Environmental & Health 2 (7) Water purveyor 1 (4) Total 28 (100) Table 8 shows the reasons provided for why no drinking water restriction or recommendation was issued in the face of a WBE. The most common reason was that the implicated facility or water source had been closed in response to the outbreak. Novometrix Research, Inc. Page 6 of 40

10 Table 8 Reasons given for not issuing a drinking water restriction or recommendation in the presence of a waterborne disease event (WBE). Reasons for not issuing a Drinking Water Restriction or Recommendation Number (%) Facility Closed / Source Shut Down 4 (50) Advisory Already in Place 1 (13) WBE Already Resolved 1 (13) Source of WBE not Identified 1 (13) Water Source Tested Negative 1 (13) Total 8 (100) Water Source The water source was surface water in 50% of WBEs, and ground water in 39%. A mix of ground and surface water accounted for the remaining 11% of WBEs (Table 13). Protozoal infections were most commonly associated with surface water, while viral and certain bacterial infections (E. coli, S. aureus and Salmonella) were most commonly associated with ground water sources, although the numbers of WBEs associated with viral and bacterial infections were small (Table 9). Table 9 Distribution of waterborne disease events (WBEs) by water source type. WBE Agent Surface & Surface Ground Water Ground Water Water (%) (%) (%) Total Giardia 9 (90) 1 (10) 0 (0) 10 Cryptosporidium 4 (57) 1 (14) 2 (29) 7 Cryptosporidium & Giardia 2 (100) 0 (0) 0 (0) 2 Toxoplasma 1 (100) 0 (0) 0 (0) 1 Campylobacter 2 (67) 0 (0) 1 (33) 3 E. coli 1 (33) 2 (67) 0 (0) 3 E. coli & Campylobacter 0 (0) 1 (100) 0 (0) 1 Legionella 0 (0) 0 (0) 1 (100) 1 Salmonella 0 (0) 1 (100) 0 (0) 1 S. aureus 0 (0) 1 (100) 0 (0) 1 Total Coliform 1 (100) 0 (0) 0 (0) 1 Norovirus 1 (25) 3 (75) 0 (0) 4 Hepatitis A 0 (0) 3 (100) 0 (0) 3 Chemical 0 (0) 1 (50) 1 (50) 2 Total 21 (53) 14 (35) 5 (13) 40 *Percentages represent row totals Surface Water The most common source of surface water was streams or rivers followed by lakes (Table 10). Eighty-four percent of watersheds in regions with a WBE associated with surface water were unprotected at the time of the outbreak (Table 11). Information on the type of activity at the time of the outbreak was available for only 12 of the 21 unprotected watersheds. Activities included the presence of wildlife (33%), heavy multiple uses (25%) and agriculture (17%). A change in weather at the time of the outbreak was reported by 54% of WBE and it was most often (70%) an increase in rain or spring runoff / thaw or a combination of the two. Novometrix Research, Inc. Page 7 of 40

11 Table 10 Distribution of waterborne disease events by surface water type. Type of Surface Water Number (%) Stream / River 12 (43) Lake 7 (25) Pond / Reservoir 4 (14) River to Reservoir 2 (7) Lake & River 2 (7) Spring 1 (4) Total 28 (100) Table 11 Type of watershed protection present at time of waterborne disease events associated with surface water. Watershed Protection Number (%) Unprotected 21 (84) Partially Protected 3 (12) Fully Protected 1 (4) Total 25 (100) Ground water Ground water source at the time of WBEs was primarily drilled (55%) or artesian wells (18.%; Table 12). In 53% of WBEs involving ground water the ground water was reported to be under the direct influence of surface water. The well-head was protected in 67% of WBEs involving ground water, and a few WBEs (36%) involved a change in the integrity of the well or aquifer prior to the outbreak. Table 12 Distribution of waterborne disease events by type of ground water. Type of Ground Water Source Number (%) Drilled Well 12 (55) Artesian Well 4 (18) Dug Well 2 (9) Mixed Ground Source 2 (9) Shallow Well 2 (9) Total 22 (100) Source water post-outbreak There were changes in water source from the time of WBEs to the time of the respective interviews. Surface water was the water source in 50% of WBEs but only 35% for the same populations at the time of interview. Conversely, ground water was the water source in 39% of WBEs but 50% for the same populations at the time of interview (Table 13). In addition to a change from surface to ground water, regions having experienced WBEs also made changes in the type of surface and ground water they used subsequent to the outbreak, for the same populations. At the time of the interview, populations having experienced WBEs were served less by river and stream surface water and more by reservoirs and lakes than at the time of the outbreaks. There was also an increase in the use of drilled wells, a decrease in artesian wells and a reduction in the number of ground water sources under the direct influence of surface water. Novometrix Research, Inc. Page 8 of 40

12 Table 13 Type of water source during waterborne disease events (WBE) and at the time of interview for the same populations. Water Source During WBE Number (%) Surface Water 23 (50) Ground Water 18 (39) Mix of Surface & Ground 5 (11) Total 46 (100) Water Source at Time of Interview Number (%) Surface Water 16 (35) Ground Water 23 (50) Mix of Surface & Ground 5 (11) Closed Facility 2 (4) Total 46 (100) Water Treatment and Distribution The most common water treatment in effect during WBEs was disinfection (46%); in 39% of WBEs there was no treatment in effect at all. Filtration was in effect in only 15% of WBEs (Table 14). Of the 28 WBEs in which disinfection was in place, chlorine was used in 75%. Table 14 Method of water treatment in place at time of waterborne disease event (WBE). Water Treatment at time of WBE Number (%) Disinfection 21 (46) No Treatment 18 (40) Disinfection & Filtration 3 (7) Disinfection, Coagulation, & Filtration 3 (7) Disinfection, Coagulation, Filtration & Reverse Osmosis 1 (2) Total 46 (100) Interviewees were asked to specify any events related to water treatment that occurred around the time of the WBE. The most commonly reported deficiency was a lack of or inadequate filtration followed by inadequate chlorination. Water treatment practices also changed between the time of WBEs and the time of the interview for the same populations. There was an increase in the use of disinfection, filtration, coagulation and reverse osmosis and a decrease in the absence of water treatment (Table 14 vs. Table 15). Water distribution was by pipe in 80% of regions before a WBE event and 79% of regions after a WBE. Novometrix Research, Inc. Page 9 of 40

13 Table 15 Method of water treatment in place at time of interview for populations having experienced a waterborne disease event (WBE). Current Water Treatment Number (%) Disinfection 18 (43) No Treatment 7 (17) Disinfection & Filtration 9 (21) Disinfection, Coagulation, & Filtration 6 (14) Disinfection, Coagulation, Filtration & Reverse Osmosis 2 (5) Total 42 (100) Table 16 shows the distribution of water treatment practices by etiologic agent for reported WBEs. Generally speaking, bacterial, viral and Giardia outbreaks tended to occur in systems having either no treatment or disinfection only. Cryptosporidium outbreaks, on the other hand, tended to occur in association with systems having some combination of disinfection and filtration. Table 16 Method of water treatment in place at the time of waterborne disease event (WBE) by agent identified No Treatment Disinfection Disinfection & filtration Disinfection, coagulation & filtration Disinfection, coagulation, filtration & reverse osmosis Giardia 4 (40%)* 5 (50%) 1 (10%) 0 0 Cryptosporidium 0 3 (43%) 0 3 (43%) 1 (14%) Cryptosporidium & Giardia 1 (50%) 1 (50%) Toxoplasma 0 1 (100%) Campylobacter 2 (67%) 1 (33%) E. coli 2 (67%) 1 (33%) E. coli & Campylobacter 0 1 (100%) Legionella (100%) 0 0 Salmonella 1 (100%) S. aureus 1 (100%) Total Coliform 0 1 (100%) Norovirus 2 (50%) 2 (50%) Hepatitis A 3 (100%) Chemical 0 1 (50%) 1 (50%) 0 0 Total *Values in parentheses represent row percentages Water Quality Monitoring Table 17 shows the distribution of water quality monitoring activities for reported WBEs. There was no routine testing at all for chlorine in 48% of regions that had a WBE, for turbidity in 57%, for coliforms / E. coli in 34% and for Giardia / Cryptosporidium in 55%. Novometrix Research, Inc. Page 10 of 40

14 Table 17 Type and frequency of water quality monitoring at time of waterborne disease event (WBE). Chlorine Number (%) Turbidity Number (%) Coliform / E. coli / Chemicals Number (%) Giardia / Cryptosporidium Number (%) Daily 1 (4) 1 (5) 1 (3) Weekly 4 (11) Biweekly 1 (4) 1 (5) Monthly 3 (9) 2 (9) Sometimes 4 (16) 7 (20) 1 (5) Yearly 2 (8) 2 (10) 2 (6) 2 (9) According to Standards 5 (20) 5 (24) 6 (17) 5 (23) Not at all 12 (48) 12 (57) 12 (34) 12 (55) Total 25 (100) 21 (100) 35 (100) 22 (100) *Values in parentheses represent row percentages Demographic Information and Health Outcomes Population Size WBEs occurred in communities with an average population of 26,969 (median 438; range 4-390,000). The mean number of cases per WBE was 654 (median 20; range 0-15,000). The mean number of laboratory-confirmed cases was 40.6 (median 13; range 0-283) (Table 18). Table 18 Demographic characteristics of waterborne disease events (WBE).. Number of People Served by Water Supply Number of People Who Became Ill Number of Lab- Confirmed Cases Mean 26, Median Standard Deviation 75,501 2, Minimum Maximum 390,000 15, Number of WBE Missing The frequency distribution of community population category size is shown in Table 19 and Figure 2. The results indicated that the majority of WBEs occurred in systems serving less than 1000 people. Table 19 Frequency and percentage of waterborne disease events (WBE) by community population. Population Size Frequency (%) (31) 101-1, (31) 1,001-10,000 7 (17) 10, ,000 6 (14) >100,000 3 (7) Total 42 (100) Novometrix Research, Inc. Page 11 of 40

15 Figure 2 Histogram of frequency of waterborne disease events (WBE) by community population size. Population size and year of outbreak WBEs were more frequent prior to 2001 although there was no clear change in the distribution of WBEs as a function of community size over time (Table 20). Table 20 Frequency distribution of waterborne disease events (WBE) by population size and year Year Population size ,000 1,001-10,000 10, ,000 >100, (75%)* (25%) (40%) 2 (40%) 1 (20%) (43%) 1 (14%) 2 (29%) 1 (14%) (33%) 1 (33%) 1 (33%) (100%) (40%) 2 (40%) 0 1 (20%) (50%) 1 (17%) 2 (33%) (100%) (100%) (100%) (50%) 1 (50%) (50%) 1 (50%) 0 Total *Values in parentheses represent row percentages Novometrix Research, Inc. Page 12 of 40

16 Population size, illness, and WBE agent Giardia outbreaks on average tended to affect communities of smaller population size and to cause fewer cases than all outbreaks combined. In contrast, Cryptosporidium outbreaks tended to affect larger communities and to cause more cases (Tables 21-23). Table 21 Size of population affected by waterborne disease events (WBE) as a function of the agent involved. Population Served by Water Supply During WBE Agent Mean Median Minimum Maximum Giardia 2, ,000 Cryptosporidium 138,643 90,000 15, ,000 E.coli Hepatitis A Table 22 Number of individuals who became ill during waterborne disease events (WBE) as a function of the agent involved. People Who Became Ill During WBE Agent Mean Median Minimum Maximum Giardia Cryptosporidium 3, ,000 E.coli Hepatitis A Table 23 Number of laboratory-confirmed cases during waterborne disease events as a function of the agent involved. Lab-Confirmed Clinical Cases Agent Mean Median Minimum Maximum Giardia Cryptosporidium E.coli Hepatitis A Novometrix Research, Inc. Page 13 of 40

17 The distribution of community size by agent was examined (Tables 24-25). Cryptosporidium outbreaks tended to occur in larger communities, while Giardia, bacterial and viral outbreaks tended to occur in smaller communities. Table 24 Frequency distribution of waterborne disease events (WBE) by population size category and agent. Population size Agent ,000 1,001-10,000 10, ,000 >100,000 Giardia 2 (25%)* 3 (38%) 3 (38%) 0 0 Cryptosporidium (57%) 3 (43%) Cryptosporidium & Giardia (100%) 0 0 Toxoplasmosis (100%) 0 Campylobacter 0 3 (100%) E. coli 2 (67%) 1 (33%) Legionella 0 1 (100%) Salmonella 0 1 (100%) S. aureus 1 (100%) Total coliform (100%) 0 Norovirus 2 (50%) 1 (25%) 1 (25%) 0 0 Hepatitis A 2 (100%) Chemical 0 1 (50%) 1 (50%) 0 0 Not identified 4 (67%) 2 (33%) Total *Values in parentheses represent row percentages Novometrix Research, Inc. Page 14 of 40

18 Table 25 Summary of population size and year for each waterborne disease event (WBE). Agent Population Year Agent Population Year Giardia Cryptosporidium Giardia Cryptosporidium Giardia Cryptosporidium Giardia Cryptosporidium Giardia Cryptosporidium Giardia Cryptosporidium Giardia Cryptosporidium Giardia Giardia unknown 1996 Cryptosporidium & Giardia Giardia unknown 1993 Cryptosporidium & Giardia E. coli 4 Toxoplasmosis E. coli E. coli Campylobacter Campylobacter Legionella Campylobacter Salmonella E. coli & Campylobacter unknown 2000 S. aureus Total coliform Norovirus Hepatitis A Norovirus Hepatitis A Norovirus Hepatitis A unknown 1995 Norovirus Chemical Unidentified Chemical Unidentified Unidentified Unidentified Unidentified Unidentified Unidentified Unknown Population size, water source, and frequency of illness. WBEs associated with surface water involved larger populations and larger numbers of cases than those associated with ground water (Tables 26-27). The average number of people who became ill was highest in communities served by surface water and lowest when served by ground water (Table 28-29) Table 26 Size of population affected by waterborne disease events (WBE) as a function of water source. Population Served by Water Supply During WBE Source Type Mean Median Minimum Maximum Surface Water 58,291 5, ,00 Ground Water 7, ,000 Surface & Ground Water 41, ,000 Novometrix Research, Inc. Page 15 of 40

19 Table 27 Frequency distribution of WBEs by community population size category and water source. Population size Source Type ,000 1,001-10,000 10, ,000 >100,000 Surface water 4 (19%)* 6 (29%) 5 (24%) 4 (19%) 2 (10%) Ground water 9 (56%) 4 (25%) 2 (13%) 1 (6%) 0 Surface & Ground water 0 3 (60%) 0 1 (20%) 1 (20%) Total *Values in parentheses represent row percentages Table 28 Number of individuals who became ill during waterborne disease events (WBE) as a function water source. People who Became Ill During WBE Source Type Mean Median Minimum Maximum Surface Water 1, ,000 Ground Water Surface & Ground Water Table 29 Number of laboratory-confirmed cases during waterborne disease events (WBE) as a function water source. Lab-Confirmed Clinical Cases Source Type Mean Median Minimum Maximum Surface Water Ground Water Surface & Ground Water Population size, water treatment, watershed protection and water quality monitoring Communities that had no treatment in place at the time of WBE tended to be small, while disinfection alone tended to be utilized in small to medium sized ones. Filtration in effect was in larger populations (Table 30). There was no relationship between watershed protection and population size (Table 31). WBE in which there was no water quality monitoring occurred in small communities only (Table 32). Table 30 Frequency distribution of waterborne disease events (WBE) by population size category and water treatment. Population size Treatment type ,000 1,001-10,001-10, ,000 >100,000 None 8 (50%)* 6 (38%) 2 (13%) 0 0 Disinfection 5 (26%) 4 (21%) 5 (26%) 4 (21%) 1 (5%) Disinfection & filtration 0 3 (100%) Disinfection, coagulation, & filtration (33%) 2 (67%) Disinfection, coagulation, filtration, & reverse osmosis (100%) 0 Total *Values in parentheses represent row percentages Novometrix Research, Inc. Page 16 of 40

20 Table 31 Frequency distribution of waterborne disease events (WBE) by watershed protection and population size category. Population size Watershed protection ,000 1,001-10,000 10, ,000 >100,000 Fully (100%)* 0 0 Partially 0 1 (33%) 1 (33%) 1 (33%) 0 Unprotected 4 (20%) 6 (30%) 3 (15%) 4 (20%) 3 (15%) Unknown 0 2 (100%) Total *Values in parentheses represent row percentages Table 32 Frequency distribution of waterborne disease events (WBE) by water quality monitoring and population size category Population Size Water Quality Monitoring ,000 1,001-10,001- >100,000 10, ,000 Yes 4 (17%)* 6 (25%) 6 (25%) 5 (21%) 3 (13%) No 8 (67%) 4 (33%) Unknown 1 (25%) 3 (75%) Total *Values in parentheses represent row percentages Age and sex of waterborne illness cases There were only seven WBEs in which information on average age of cases was provided, and this was an estimate by the interviewees in some cases (Table 33). The mean of the average age per WBE was 38 years (median 34; range 29-65). The range of case ages was 0.2 to 97 years. Approximately 50% of the cases were women. Table 33 Age and sex of cases in waterborne disease events (WBE). Age & Sex of Cases Mean Median Std. Deviation Minimum Maximum n Missing Average Age Minimum Age Maximum Age Percent Female Case definition, hospitalizations, and fatalities. The case definition used for WBEs varied among regions and outbreaks, but consisted of a combination of symptoms, laboratory confirmation, water use, and relevant time frame and geographic area (Table 34). Hospitalizations were required in 38% of WBEs (Table 35), and the mean duration of hospitalization was 12 days (median 2 days; range 1-65 days). Fatalities were reported in one WBE (Table 36). There was only 1 WBE in which extra-gi clinical syndromes were reported; the identified syndromes included retinochoroditis and lymphadenopathy. Novometrix Research, Inc. Page 17 of 40

21 Table 34 Case definition utilized during waterborne disease events (WBE). Case Definition for WBE Frequency (%) GI Symptoms 8 (25) Severe Symptoms 1 (3) Lab Confirmation 9 (28) CDC Guidelines 1 (3) Symptomatic & Used Suspect Water 2 (6) Symptomatic in WBE Timeframe & Area 4 (13) Symptomatic & Lab Confirmation 7 (2 Total 32 (100) Table 35 Frequency of waterborne disease events in which hospitalization was reported:. Hospitalizations Frequency (%) Yes 9 (38) No 13 (54) In seniors home 2 (8) Total 24 (100) Table 36 Frequency of waterborne disease events in which fatalities were reported. Deaths Frequency (%) Yes 1 (3) No 30 (97) Total Factors contributing to waterborne disease events Interviewees identified factors that may have contributed to waterborne events, and multiple factors were often indicated (Table 37). Inadequate treatment was cited as the most common contributing factor (64%), followed by lack of source water protection (39%), animals in the watershed (36%), and precipitation (32%). Table 37 Frequency of responses regarding contributing factors to waterborne disease events. Contributing Factors* Frequency (%) Precipitation 14 (32) Contamination at Water Source Water Treatment Deficiencies Cross Contamination in Water Distribution Spring thaw / run-off 7 (16) Flooding 3 (7) Lack of source water protection 17 (39) Animals in the watershed 16 (37) Other 7 (16) Treatment failure 7 (16) Inadequate treatment 28 (64) Other 5 (11) Broken pipe(s) 3 (7) Post-treatment contamination 5 (11) Cross connection 0 (0) Turbidity 10 (23) Human error 5 (11) Other No contributing factors identified 1 (2) *Multiple responses possible Novometrix Research, Inc. Page 18 of 40

22 The study requested additional information on factors believed to have contributed to WBEs listed in Table 37. Wildlife accounted for the majority of animals identified as contributing to WBEs. Other sources of contamination of source water was principally septic and / or sewage. Causes of treatment failure were usually unspecified. Cause of inadequate treatment was most often not specified, although no treatment and no filter were cited frequently (Table 38). Table 38 Frequency of responses that specified contributing factors* in waterborne disease events from Table 37. Type of Animals in the Watershed* Frequency (%) Wildlife 10 (6 Yes-Unspecified 3 (19) Cattle / Agriculture 2 (13) Wildlife & Agriculture 1 (6) Other Contamination at Water Source Frequency (%) Septic / Sewage too Close 4 (57) Human Activity 1 (14) Upstream Water Contamination 1 (14) Heat & Septic / Sewage 1 (14) Treatment Failure Frequency (%) Yes-Unspecified 4 (57) Chlorine Turned Off 1 (14) Inadequate Chlorination 1 (14) No Flocculation Blanket & Crack in Plant 1 (14) Inadequate Treatment Frequency (%) Yes-Unspecified 9 (32) No Treatment 8 (29) No Filter 6 (21) Chlorination Inadequate 3 (11) Recycled Filter 1 (4) No Retention Pond 1 (4) Other Water Treatment Deficiencies Frequency (%) Backflow Minnow Tank 1 (20) Sewage Upstream 1 (20) No Treatment 1 (20) No Water Monitoring 1 (20) Yes-Unspecified 1 (20) *Multiple responses possible Novometrix Research, Inc. Page 19 of 40

23 Table 39 shows the relationship between contributing factors and community population size category. 10, ,000 Contributing factors* Frequency Frequency Frequency Frequency Frequency % % % % % Precipitation 6 46% 2 15% 1 17% 1 17% 2 67% Spring 1 8% 2 15% 1 17% 1 17% 2 67% thaw/run-off Flooding 0 0% 2 15% 0 0% 0 0% 0 0% Lack of 5 39% 4 31% 4 67% 2 33% 1 33% source protection Contamination at Water Source Water Treatment Deficiencies Cross Contamination in Water Distribution Other Table 39 The frequency of waterborne disease events (WBE) by population size categories and contributing factors. Population size 1,001-10, ,000 >100,000 Animals in the watershed % 5 83% 3 50% 1 33% Other 2 15% 2 15% 2 33% 0 0% 1 33% Treatment 4 31% 1 8% 0 0% 1 17% 0 0% failure Inadequate 7 54% 9 69% 4 67% 3 50% 3 100% treatment Other 2 15% 2 15% 0 0% 1 17% 0 0% Broken pipe(s) 1 8% 1 8% 0 0% 0 0% 1 33% Posttreatment 2 15% 2 15% 0 0% 0 0% 1 33% contamination Cross 0 0% 0 0% 0 0% 0 0% 0 0% connection Turbidity 3 23% 2 15% 1 17% 1 17% 1 33% Human error 0 0% 3 23% 0 0% 0 0% 1 33% No factors 0 0% 0 0% 0 0% 1 17% 0 0% *Multiple responses possible Additional Resources Used During Waterborne Disease Events Additional expert resources relied on by local public health personnel during WBE are listed in Table 40. Most frequently consulted were various local experts, the provincial epidemiologist and water treatment experts. Twenty percent of respondents said no additional resources were consulted as part of WBE investigations. Details of local experts and other resources consulted during WBEs are shown in Table 41. Table 40 Additional resources brought in to assist with waterborne disease event investigations. Additional Resources Frequency (%) Local Expert 21 (50) Provincial Epidemiologist 20 (486) Water Treatment Personnel 14 (33) No Additional Resources 9 (21) Other 9 (21) Field epidemiologist 8 (19) *Multiple responses possible Novometrix Research, Inc. Page 20 of 40

24 Table 41 Details of types of local experts and Other resources brought in to assist in waterborne disease event investigations. Other Resources Frequency (%) Public Health Staff 3 (33) Municipal Affairs Staff 2 (22) Conservation Staff 1 (11) Engineers 1 (11) Federal Epidemiologist 1 (11) Engineers & Other Consultants 1 (11) Local Experts Frequency (%) Provincial Health / Environment Staff 10 (48) Yes-Unspecified 7 (33) Chief Environmental Health Officer 2 (10) Physicians 1 (5) Staff from Other Public Health Units 1 (5) *Multiple responses possible Evidence for Drinking Water as Source of Outbreaks The type of evidence used to determine that WBEs were waterborne is shown in Table 42. The evidence frequently included identification of the same pathogen in water as in clinical cases (63%), a failure in water quality (42%), and epidemiologic evidence (46%). Table 42 Type of evidence that suggested that WBEs were waterborne. Type of Evidence Count (%) Pathogen Identified in Cases and Water 26 (63) Water Quality Failure 17 (42) Descriptive Epidemiology 17 (42) Water Treatment Problem But No Pathogen Found 4 (10) Analytical Epidemiologic Study 2 (5) *Multiple responses possible Prevention of Future WBEs A series of questions, both closed- and open-ended, addressed WBE prevention. Actions to prevent future waterborne events Participants were asked to describe actions that were taken to prevent future waterborne events. Some regions took multiple steps to prevent waterborne events. Many of the participants reported that they changed their water source or upgraded their treatment system (Table 43). Table 43 Actions taken to prevent future waterborne events (WBEs). Actions Taken to Prevent Future WBE Frequency (%) Upgrade / change treatment system 24 (56%) Education / study / assessment 12 (28%) Changed water source 28 (65%) Changed / improved policy, reporting, monitoring 13 (30%) *Multiple responses possible Following are examples of the type of open-ended responses provided: Novometrix Research, Inc. Page 21 of 40

25 1. Upgraded, added, or altered water treatment systems a. Added UV, filtration, b. Turbidity monitoring system c. Shock treated well or disinfected system. 2. Education / study / examination / assessment a. Public and staff training b. Conducted a study of WBE prevention approaches c. Assessed / evaluated their system 3. Changed water source or added protection to water source a. New well b. Changed source of water c. Stopped use (closed facility) d. Maintained boil water advisory until safe e. Covered / protected reservoir 4. Change / improve policy, reporting, monitoring a. Increased monitoring of water quality / pathogens b. Changed inspection of water systems Effectiveness of actions In addition, participants were asked about the effectiveness of their actions to prevent WBEs. The majority found the actions they took to prevent future waterborne events to be effective (Table 44). Table 44 Effectiveness of actions taken to prevent future waterborne events (WBEs). Effectiveness of Actions to Prevent WBE Frequency (%) Yes 29 (91) No - had BWA since 2 (6) No - had outbreak since 1 (3) Total 32 (100) Modification or creation of policy to prevent waterborne disease events The majority of regions (88%) created or modified policies and procedures to prevent additional waterborne disease events as a result of the reported outbreak. These usually involved multiple agencies, with the most frequently reported being the Provincial Department of Health or Environment and the public health unit or regional health authority (Table 45). Novometrix Research, Inc. Page 22 of 40

26 Table 45. Policies and procedures developed to prevent future waterborne events (WBEs), the departments involved in the process, and the policies and procedures that were developed. Policies & Procedures to Prevent WBE Frequency (%) Yes 30 (88) No 4 (12) Total Departments / Agencies Involved in Process Frequency (%) Municipality / city 5 (20) Public health office / regional health 10 (40) authorities Provincial agency (health / environment) 23 (92) Water purveyor 1 (4) Policies & Procedures Developed Frequency (%) Water source 5 (19) Boil water advisory/order 2 (7) Surveillance 2 (7) Inspection / water quality monitoring 7 (26) Treatment 11 (41) Response to outbreak 2 (7) Other initiative 5 (19) *Multiple responses possible The policies and procedures that were created to prevent future waterborne events are elaborated below. The most common policies and procedures developed were for treatment (41%) and inspection or water quality monitoring (26%). 1) Water Source a. Protection b. Alter source and maintain surface water for emergency use c. Restrictions related to potential contamination d. Address ground water under influence of surface water 2) Boil water policy / restrictions 3) Surveillance 4) Inspection / water quality monitoring of drinking water and sewage a. Municipal inspection modify / invoke b. Privately held publicly utilized facilities (camps) - address 5) Drinking Water Regulations or Treatment Policy 6) Response to outbreak 7) Other initiatives Creation and modification of policies for waterborne event investigation Policies and procedures created to modify or address investigation or management of future waterborne events were reported by 71% of respondents (Table 46). Table 46 Policies and procedures developed to investigate or manage future waterborne events (WBEs). Policies and Procedures for WBE Investigation Frequency (%) Yes 20 (71) No 8 (29) Total 28 (100) Novometrix Research, Inc. Page 23 of 40

27 The policies and procedures developed to address investigation or management of future waterborne events included: 1) Increased sampling 2) Restructured investigation approach 3) Changed approach a. Spend more time understanding water quality and treatment b. Use resources more appropriately 4) Specialized health inspectors 5) Upgraded groundwater protocols 6) Education a. Supplied fact sheets for education of private well owners b. Ensured up-to-date contact list Were actions taken to prevent future WBE congruent with contributing factors? Table 47 shows the relationship between contributing factors and the actions taken to prevent future WBE. For each contributing factor a range of actions were taken, reflecting that appropriate action is multifaceted and depends on the specifics of each situation. When examining this table, one must keep in mind that contributing factors and actions to prevent future WBE were both multiple response answers. So, for example a region that cited animals in the watershed as a contributing factor may have also cited treatment failure, and hence actions relevant to both would be appropriate. Table 47 Frequency of waterborne disease events (WBE) as a function of contributing factors and actions taken to prevent future outbreaks. Actions Taken to Prevent Future WBE Contamination at Water Source Contributing factors Upgrade/ change treatment Frequency (%) Education/ study/ assessment Frequency (%) Changed water source Frequency (%) Changed/ improved policy, reporting, monitoring Frequency (%) Precipitation 8 (62%) 5 (39%) 9 (69%) 4 (31%) Spring thaw/run-off 6 (86%) 3 (43%) 2 (29%) 3 (43%) Flooding 2 (67%) 1 (33%) 2 (67%) 1 (33%) Lack of source 10 (63%) 5 (31%) 12 (75%) 6 (38%) protection Animals in the watershed 10 (67%) 4 (27%) 11 (73%) 3 (20%) Other 5 (71%) 1 (14%) 5 (71%) 2 (29%) Treatment failure 3 (43%) 2 (29%) 6 (86%) 3 (43%) Inadequate treatment 17 (63%) 8 (30%) 18 (67%) 8 (30%) Water Treatment Deficiencies Other 1 (33%) 3 (100%) 1 (33%) 2 (67%) Cross Broken pipe(s) 2 (67%) 2 (67%) 1 (33%) 2 (67%) Contamination Post-treatment 2 (67%) 1 (33%) 2 (67%) 1 (33%) in Water contamination Distribution Cross connection Other Turbidity 8 (89%) 4 (44%) 6 (67%) 4 (44%) Human error 3 (60%) 4 (80%) 3 (60%) 4 (80%) No contributing factors *Multiple responses possible Novometrix Research, Inc. Page 24 of 40

28 Risks Predisposing to WBEs An overwhelming majority of respondents (88%) reported that there were risks that predisposed their region to waterborne events (Table 48). Table 48 Risks that predisposed regions to waterborne events (WBEs). Risks that Predispose Area to WBE Frequency (%) Yes 37 (88) No 5 (12) Total 42 (100) The risks were varied and included the following: 1) Environmental & Cultural a. Human activity b. Agricultural activity c. Wildlife activity d. Industry e. Spring run-off f. Cultural disbelief in safety of treatment 2) Monitoring a. Lots of small systems b. Large geographic area with small population to monitor c. Budgets inadequate 3) Source a. Surface water b. Turbidity c. Shallow wells d. Old or damaged wells e. Poorly located wells (i.e. in barnyard) f. Chemical naturally present in water 4) Treatment facilities a. Water treatment b. Sewage treatment c. Placement of septic systems close to source d. Old treatment facilities / equipment e. Inexperienced operators Drinking Water Programs in Place Almost all the respondents (98%) answered that programs to reduce the risk of a WBE had been in place prior to the interview (Table 49). Of those that responded, 74% said that the program was currently in place. Table 49 Programs in place to reduce the risk of waterborne disease events (WBE). Programs to Reduce Risk of WBE Frequency (%) Yes 40 (98) No 1 (2) Total 41 (100) Novometrix Research, Inc. Page 25 of 40